Unusual Tropane Alkaloid Pattern in Two African Convolvulaceous Species. Phytochemistry and Chemotaxonomy of the Convolvulaceae, Part 20 [1]

An unusual and complex tropane alkaloid pattern has been detected in the root bark of Astripomoea malvacea and in the whole plant of Falkia repens (Convolvulaceae) by GC-MS analysis. The specific profile of both species is characterized by the presence of aliphatic 3- acyloxytropanes/-nortropanes (exclusively in A. malvacea; predominantly in F. repens in cooccurrence with a few aromatic as well as arylalkyl acyl congeners). The principal alkaloid of A. malvacea, astrimalvine A N-oxide [3β -(3-tigloyloxy-2-methylbutyryloxy)tropane N-oxide], isolated and structurally elucidated by detailed spectroscopic analysis, represents the first N-oxide of a 3β -tropanol derivative in the Convolvulaceae. Its minor tertiary congener astrimalvine B [3β -(3-hydroxy-2-methylbutyryloxy)tropane] turned out to be a metabolite of both convolvulaceaous species. This is the first phytochemical report on the African genera Astripomoea and Falkia.